Don't take this the wrong way but, How big is the scene? Are you waiting long enough for it to render? If it's complex then it could be quite a while before you see anything!
P7 does seem to have this little trick of saying "rendering" and then the preview window goes blank for a bit before you see anything, does on mine anyway [LOL].
Sorry if I'm teaching granny to suck eggs but I don't know what else to suggest!!

Injustice will be avenged.
Cofiwch Dryweryn.